An investigation into the effect of surface area on the enzyme catalase.

Authors Avatar

An investigation into the effect of surface area on the enzyme catalase.

Catalase

By Andy Mc Namee


The effect of surface area on the activity of catalase in potatoes

Planning:

*Hypothesis* hydrogen peroxide will breakdown to oxygen and water in the presence of Catalase. The reaction will increase with increasing enzyme concentration when molecules of hydrogen peroxide are freely available. However, when molecules of the substrate are in short supply, the increase in rate of reaction is limited and will have little effect.

Enzymes are globular protein biological catalysts; it is called a catalyst because it helps speed up chemical reactions. As enzymes are globular, this means that they are coiled up into a 3-dimensional shape they have hydrophilic side chains on the outside to ensure that they are soluble. If they weren’t soluble then they wouldn’t be able to combine with substrates and help break them down. Enzymes also contain a depression or a cleft inside them, this is called the active site. This is where substrates are broken down for example the enzyme catalase has an active site so it will break down hydrogen peroxide into water and oxygen. The active site can also join two substrates together, for example a dipeptide. The active site isn’t just a random hole, it has a specific size and shape, because of this precise cleft, the enzyme will only break down certain substrates, normally only one. Take for example; hydrogen peroxide into water and oxygen, this breakdown is caused by the enzyme catalase holding the hydrogen peroxide molecule in place and then breaks down the substrate whilst it is being held into place, by bonds between the side chains and the substrate. As the enzyme is only holding the substrate into place it isn’t affected greatly and can carry this process out many times. Due to this much organised method of breaking down substrates, it can also be carried out very quickly. I have found out that hydrogen peroxide can be broken down into hydrogen and water 107  molecules per second.

        In order for enzymes to work to their optimum potential there has to be sufficient substrates to be broken down, the enzyme may be working at its potential, in near perfect conditions, but if there is a lack of substrate to be broken down then some of the enzymes won’t be working, therefore the output won’t be their maximum. By increasing the surface area on the potato, it allows more catalase to react with the hydrogen peroxide, allowing the maximum output to be found.


In the above table, it shows how increasing the surface area, increases the rate of reaction. As you can see, in the above table, as the surface area of the potato increases, it allows more hydrogen peroxide molecules to bind with the potato as there is more room. By allowing more hydrogen peroxide and catalase to combine, it means that there are more catalase enzymes to break down the hydrogen peroxide.

For example, if I had a piece of potato, 2cm long, and a radius of 0.5cm,  the surface area [2πr(r+h)] would be 7.85cm2, but if I divided up the potato into 10 pieces, the surface area would then be, 21.99cm2. As you can see, from cutting the cylinder of potato into 10 discs it increases the surface area by nearly 3 times. This allows 3 times the amount of catalase to react with the hydrogen peroxide surrounding it.

An enzyme will breakdown the substrate by using its active site, each different enzyme’s active site will have a specific shape for a specific substrate. In my case, the enzyme catalase, its active site will have the same shape as the substrate, hydrogen peroxide. This is how they work:

        By using secondary research from  I found out that the enzyme catalase is found in an organelle called a peroxisome present in nearly all aerobic cells, it protects the cell from the toxic effects of hydrogen peroxide by catalyzing it into oxygen and water making the hydrogen peroxide a lot less damaging to the potato. As it is found in aerobic cells, this means that there should be a good supply of oxygen present during the experiment, otherwise the enzyme won’t be working at its full potential.

Join now!

I believe that as the surface area increases, it will mean that more oxygen will be produced, until all the hydrogen peroxide has been broken down and the enzymes can’t break any more down, the amount of oxygen produced will decrease until there isn’t any being produced. Or, there aren’t enough catalase enzymes in a certain surface area, meaning that ALL the enzymes will be working, in a sufficient amount of hydrogen peroxide, so the amount of hydrogen peroxide given off will plateau, because it is the maximum amount of oxygen that can be given off by using that ...

This is a preview of the whole essay